The error -- coupled with a depressurization warning and then unexplained radio silence from the cockpit -- led to two jet fighters being scrambled to escort the Boeing 737 to land at Vienna's Schwechat airport.

The passenger plane had been flying from Frankfurt to Istanbul when panicked passengers saw oxygen masks fall from the ceiling after it was hit by a pressurization problem.

The pilot -- who had asked to make an emergency landing -- apparently inadvertently activated the hijack alarm as he responded to the problem, police said, confirming a report on the website of the daily Kurier newspaper.

Authorities stepped down from their hijack alert status 40 minutes after the plane landed, Kurier said.

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